1. Field of the Invention
The present invention relates to a disconnection switch which constitutes a main apparatus of a switchgear for receiving/distributing electric power, and more particularly, to a solid insulated disconnection switch unit and solid insulated disconnection switch including the unit capable of enhancing stability by applying a solid insulating construction on all over the disconnection switch for reducing an entire size thereby enhancing a spatial efficiency.
The present invention also relates to a solid insulated switchgear capable of having a smaller size than the conventional gas-insulated switchgear, capable of simplifying manufacturing, maintaining, and repairing processes, and capable of implementing various configurations by combining a plurality of units each formed of standardized components or parts to one another.
2. Description of the Background Art
A disconnection switch serves to isolate an electric circuit after removing an electric load current, and is different from a load break switch in that the disconnection switch does not switch the circuit of load current. The disconnection switch is a switch which is installed in a power-transmission site or a substation to switch the circuit when a connection to a main circuit need to be changed under the state without load with the circuit breaker opened.
The disconnection switch is housed in an airtight metal container whose inside is filled with an insulating material such as air, or an SF6 (6 sulfur fluoride) gas having more insulating effect than air, in order to keep the main circuits insulated from each other or the earth.
The disconnection switch comes in many switching structures, which switches the main circuit, with no electric load. The disconnection switch within the gas insulated switchgear using the SF6 gas, as shown in FIG. 1A-1B and 2, is now described.
FIG. 1A is a front view illustrating that the disconnection switch according to the related art is in an opened state, FIG. 1B is a front view illustrating that the disconnection switch according to the related art is in a closed state, and FIG. 2 is a plan view of the disconnection switch as shown in FIG. 1A.
The disconnection switch includes main buses 201 provided in parallel inside a container 210 so as to perform a gas insulation, a main circuit fixed contactor 230 fixed to the main bus 201, a main circuit movable contactor 220 which rotates to be connected to or be separated from the fixed contactor 230 and is coupled to a bushing 202, a driving mechanism 260 which drives the movable contactor 220, a power transferring shaft 240 which transfers power generated from the driving mechanism 260, and an insulating linker 250 which transfers the power to and maintains an insulation from the main circuit.
Operation of the disconnection switch will be explained.
FIG. 1A is a front view illustrating that the disconnection switch according to the related art is in a disconnected state (an opened state). The disconnected state means that the disconnection switch is disconnected from the main circuit, more specifically that the movable contactor 220 is disconnected from the fixed contactor 230.
The driving mechanism 260 driven by a motor, when receiving an electric signal for closing operation in the disconnected state, rotates the power transferring shaft 240, for example, by 50 degrees counterclockwise. As a result, the insulating linker 250, which is connected to the power transferring shaft 240 using a pin, moves downwards and rotates by 50 degrees counterclockwise to a position where the insulating linker 250 is positioned as shown in FIG. 1B. Accordingly, the movable contactor 220 is coupled to the fixed contactor 230, so that the main bus 201, the fixed contactor 230, the movable contactor 220, and the bushing 202 are electrically connected to each other, making it possible to normally operate the switchgear. This is hereinafter referred to as “the closed state”
Conversely, in order to disconnect the main circuit from the closed state, the power transferring shaft 240 rotates in opposite direction as above mentioned direction. As a result, the insulating linker 250 and the movable contactor 220 connected to the power transferring shaft 240 rotate to create the disconnected state that the fixed contactor 230 and the movable contactor 220 are separated from each other.
In the switchgear for receiving/distributing electric power having double main buses, the disconnection switch is provided for each of the main buses. So, when one main bus is in trouble, it is possible to provide electric power using the other main bus. The arrangement of the double main buses in the switchgear depends on the positional relationship between the main bus and the container 210. The main buses are usually provided in parallel to each other.
The recent trend towards automation, miniaturization, high reliability, and low cost requires the switchgear including the above disconnection switch to be developed in such a way as to follow the recent trend.
To that end, in addition to performing a basic function of changing the connection to the main circuit with no electric load, the disconnection switch has to minimize an insulation space required between the main circuits (corresponding to phases) and between the main circuit and the earth to reduce the size of the switchgear.
However, the use of the gas places as the insulating material imposes a limitation on reducing the size of the switchgear including the disconnection switch.
The reduction of the size of the disconnection switch has been achieved by providing insulating solid material barriers between some components of the disconnection switch instead of using the insulating gas, or increasing the gas pressure to maintain the insulation between the components of the disconnection switch. This makes it possible to largely reduce the size of the disconnection switch and requires everyday maintenance operations such as the cleaning of main buses, the checking of the gas pressure, or the like. The use of SF6 gas as the insulating gas in the disconnection switch is prohibited worldwide, because SF6 gas is the main factor increasing the atmosphere temperature.
The solid insulated switchgear according to the related art will be explained with reference to FIGS. 3 and 4
FIG. 3 is a circuit view showing a configuration of a switchgear system in accordance with the related art, and FIG. 4 is a sectional view showing a switchgear having a main unit according to a first embodiment of the related art. Referring to FIG. 3, the switchgear system in accordance with the related art includes a main unit for receiving electric power which is designated “MAIN” for a divided circuit portion, a feeder unit for supplying a current to a load which is designated “FEEDER” for a divided circuit portion, a measuring unit for measuring a voltage of a main bus which is designated “MEASURING” for a divided circuit portion, a section unit for separating the main bus from a circuit which is designated “SECTION” for a divided circuit portion, and a tie unit for connecting the two main buses to each other which is designated “TIE” for a divided circuit portion. Differently from FIG.3, if a single main bus is implemented, the tie unit is not required.
Referring to FIG. 3, the two upper lines represent two main buses on the power source side. The main unit includes a first disconnection switch (left side) and a second disconnection switch (right side) respectively connected to the two main buses that connect or disconnect a circuit, an earth switch (ES) connected to the first disconnection switch that grounds or disconnects a circuit, a circuit breaker (Vacuum Circuit Breaker, abbreviated as VCB hereinafter) commonly connected to the first and second disconnection switches that switches a circuit, a lightning arrestor (abbreviated as LA) to which the VCB is commonly connected for grounding lightning to the earth, a current transformer (CT) that measures a current of a circuit, and a potential transformer (abbreviated as PT hereinafter) that measures a potential (voltage) of a circuit.
Referring to FIG.3, the feeder unit has the same configuration as the main unit except that the PT is not provided.
Referring to FIG.3, the measuring unit includes a first disconnection switch (left side) and a second disconnection switch (right side) respectively connected to the two main buses that connect or disconnect a circuit, and a potential transformer respectively connected to the first and second disconnection switches, which measures each potential (voltage) of the two main buses.
Referring to FIG. 3, the section unit includes a third disconnection switch (the most left side DS connected to the upper main bus) connected to one of the two main buses that connect or disconnect a circuit; an earth switch (the most left side ES) connected to the third disconnection switch that grounds or disconnects a circuit; a fourth disconnection switch (a middle DS connected to the upper main bus) to which the third disconnection switch is connected, and which connects or disconnects the circuit; an earth switch (a middle ES) connected to the fourth disconnection switch, and which grounds or disconnects the circuit; a circuit breaker (the most left side VCB) connected between the third disconnection switch and the fourth disconnection switch, and which connects or disconnects the circuit; a current transformer (CT) (the right CT) connected between the circuit breaker and the fourth disconnection switch, and which measures an amount of a current flowing on the circuit; a fifth disconnection switch (left DS connected to the lower main bus) connected to the other main bus of the two main buses, and which connects or disconnects the circuit; an earth switch (the second ES from the left side) connected to the fifth disconnection switch, and which grounds or disconnects the circuit; a sixth disconnection switch (the most right side DS connected to the lower main bus) connected to the main bus to which the fifth disconnection switch is connected, and which connects or disconnects the circuit; an earth switch (the most right side ES) connected to the sixth disconnection switch, and which grounds or disconnects the circuit; a circuit breaker (the most right side VCB) connected between the fifth disconnection switch and the sixth disconnection switch, and which connects or disconnects the circuit; and a current transformer (the left CT) connected between the circuit breaker (the most right side VCB) and the fifth disconnection switch, and which measures an amount of a current flowing on the circuit.
Referring to FIG. 3, the tie unit includes a seventh disconnection switch (the left DS connected to the upper main bus) connected to one main bus of the two main buses, and which connects or disconnects the circuit; an earth switch (the left ES) connected to the seventh disconnection switch, and which grounds or disconnects the circuit; an eighth disconnection switch (the right DS connected to the lower main bus) connected to the other main bus of the two main buses, and which connects or disconnects the circuit; an earth switch (the right ES) connected to the eighth disconnection switch, and which grounds or disconnects the circuit; a circuit breaker (VCB) connected between the seventh disconnection switch and the eighth disconnection switch, and which connects or disconnects the circuit; and a current transformer connected between the circuit breaker (the VCB) and the eighth disconnection switch, and which measures an amount of a current flowing on the circuit.
The switchgear according to the related art does not always require all of the five units, but selectively requires the five units according to a user's demand. Generally, the switchgear basically includes the main unit for receiving electric power, the feeder unit for feeding electric power to a load, and the measuring unit for measuring electrical potential. The switchgear may selectively include the section unit and the tie unit. All of the five units need to be individually manufactured by a manufacturer so as to meet a customer's various demand. FIG. 4 is a section view showing a switchgear having a main unit according to one embodiment of the related art.
Referring to FIG. 4, two upper and lower main buses 83 are respectively connected to a circuit breaker 101 via 3-way switches 100a and 100b implemented by combining an earth switch and a disconnection switch to each other. Another side of the circuit breaker is connected to a cable 105, thereby receiving electric power or feeding electric power to a load. An insulating spacer 51 for preventing an abnormal current from being transmitted and for dividing a sealing chamber of SF6 gas is disposed between the 3-way switches 100a and 100b and the circuit breaker 101. A driving source assembly 61 for driving the 3-way switches 100a and 100b, and a driving mechanism 103 for driving the circuit breaker 101 are provided.
A current transformer (CT) is disposed to surround the cable 105 so as to measure a current applied to the cable 105.
Operation of the conventional switchgear having a main unit will be explained.
Referring to FIG. 4, when a middle movable contact of the 3-way switches 100a and 100b moves to be connected to the lower main bus (power source side terminal), the circuit from the main bus 83 to the cable 105 is closed under a state that a contactor of the circuit breaker 101 is connected to the middle movable contactor. If the middle movable contactor of the 3-way switches 100a and 100b is connected to a ground terminal 33a, the circuit is grounded.
Under a state that the middle movable contact (not shown) of the 3-way switches 100a and 100b moves to be connected to the lower main bus (power source side terminal) (closed circuit state), when an abnormal current (a large current) flows onto the circuit and a signal due to the abnormal current is transmitted to a controller (not shown) from the CT, the controller drives the driving mechanism. Accordingly, the circuit breaker 101 is operated at a position to break the circuit, and the circuit from the main bus to the cable (load side) is opened.
In case of switching a main bus when the circuit is maintained or repaired or in no-load state, the circuit breaker 101 is operated to a position for breaking the circuit. Then, the middle movable contactor (not shown) of the 3-way switches 100a and 100b moves to be connected to the ground terminal 33a, thereby flowing remaining current to the earth. Then, the driving source assembly 61 is operated thus to move the middle movable contactor of the 3-way switches 100a and 100b to a closed state that the circuit is connected to no terminal or no main bus as shown in FIG. 4. Then, an operator can repair and replace the circuit, and cuts the main bus.
However, the gas-insulated switchgear according to the related art has the following problems.
First, since SF6 gas for performing an insulation is harmful gas influencing on global warming, usage of the SF6 gas has been limited worldwide.
Second, the gas-insulated switchgear according to the related art is not size reduced, the components are not standardized, and each unit such as the disconnection switch, the earth switch, and the circuit breaker is not modularized. Accordingly, it takes a lot of time to manufacture and repair the switchgear, and the components do not have extensibility for the future additional installation according to various conditions.